Electrooptical system



May 21, 1935. H. E. IVES ELECTROOPTICAL SYSTEM Filed Och-ll, 1930 2 Sheets-Shet 1 Wm NW Q 0 mm 9w & mm mm mm P Q Q W m mm vw Q S x MN; -i a w INVENTO/P h. L. IVQS A TTO/PNEY May 21, 1935. H. E. IVES 2,001,730

ELECTROOPTICAL SYSTEM Filed Oct. 11, 1930 2 SheetsSheet 2 INVENTOR H. E. IVES 8V z A TTO/PNEV Patented May 21, 1935 UNITED STATES PATENT OFFICE ELECTROOPTICAL SYSTEM Herbert E. Ives, Montclair, N. J., assignor to Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation of New York Application October 11, 1930, Serial No. 487,967

20 Claims. (Cl. 178-6) The present invention relates to electrooptical is selective of light of a different color, whereby systems and more particularly to methods of and they are activated to cause image currents cormeans for controlling the production of signal responding to the diflerent colors to be respeccurrents corresponding to pictures. tively transmitted over different communicat- It has heretofore been suggested to analyze a ing channels. The respective image currents en- 5 photographic record by passing light through sucergize separate light sources, each of which supcessive elemental areas of the record to a light plies light of the respective colors, and of a presensitive device. It has also been proposed to determined intensity to producea composite light illuminate successive elemental areas of a colored beam, which is scanned to produce an image corl0 record and to direct the light reflected from each responding in subject matter and color to the elemental area to a plurality of light sensitive photographic record. electric devices selective of different colors to The present invention also contemplates a syscause the production of image currents, which are tem in which successive elemental areas of a used to control the production of a similarly colphotographic record, which has been colored or ored record. has color characteristics, are projected upon a 15 The prior art includes a picture transmission diifusely reflecting or transmitting screen to prosystem comprising a film having color characvide separate beams of light to activate a pluteristics for controlling the light supplied to a rality of light sensitive devices, selective of difsingle photoelectric cell which is activated to proferent colors, to cause the production of separate duce picture currents that are supplied to asingle image currents, which are used to control the 20 light source for illuminating a lenticulated senproduction of an image in colors. In accordance sitized photographic film to produce a record at with this aspect of the invention the photoa receiver. It is stated that the invention may be graphic record may be moved continuously across used to produce picture or television images in a slot in a stationary baflle through which succolor. However, the disclosure does not embody cessive unit lines of the record are projected 25 means at the transmitter for separately controlto occupy the same position on the screen and ling the value of the picture currents correspondelemental areas of each line may be successively ing to the different colors which combine to proscanned by a movable member having apertures, duce the color characteristics of elemental areas or the successive elemental areas may be sepaof the film, nor means at the receiver for supplyrately projected to occupy the same position on 30 ing controllable amounts of light of the different the screen. In either case, each frame of the colors which must be combined to duplicate the record is projected on the screen at a rate within color characteristics of the transmitted film. the period of persistence of vision.

Hence such system cannot be operated to effect According to this invention in one aspect, a

the result set forth. moving beam of light is utilized to scan a photo- 35 An object of the invention is to provide a novel graphic film or pictorial transparency in such method o and apparatus r scanning a picture. manner that light, modulated in accordance with n t Object is to utilize a Photographic the characteristics of the picture is projected on 0rd, having color characteristics, in television sysa, diffusely reflecting screen and light reflected 40 temS fo contro l the production of a plurality from the screen is directed to light sensitive elec- 40 of image currents respectively corresponding to tric means, which is thereby activated to cause different colors, whereby an image in color of the the production of a signal current varying as the sublect photograpmcany recorded may be characteristics of successive elemental areas of duced the picture. 4o In accordance with one embodiment of the 111- A description of the invention follows and is vention, light of constant intensity passes through unit lines of a colored photographic record, and i m the atifached; drawmgs' m whlcl} a lens for projecting a colored image of each line 1 d1ag ramm?'t1cany Illustrates system in the plane of a moving image member having volvmg the Invent-10nslots for scanning each line to produce a moving Figs- 2, 3 and 4 a perspective VIEWS of 80811- 50 beam of light, colored in accordance with the nine appara us which mayb su st tut d f at color characteristics of successive elemental areas Shown in of the record, which is projected on a plurality of As shown in Fig. 1, light of constant intensity light sensitive electric devices, arranged singly or from the source I is projected by a lens 2 upon 5 in groups, each of which, or each group of which, the slot 5 in the mask 6 and passes through the colored film I, which is continuously driven at a definite rate transversely of the slot 5.

The film I may carry a colored picture, produced by the Technicolor or similar process, and is moved continuously across the slot by a suitable driving unit.

Lens 3 focuses an image of the slot 5 in the plane of the disc 9 provided with slots III which sweep across the image of slot 5 to produce a beam of light corresponding in. color to successive elemental areas of the film. A magnified image of the beam is projected by the lens I upon mirrors l2 and I3 and the light sensitive device I4. Mirrors I2 and I3 direct the light rays incident upon them to light sensitive devices I5 and I6, respectively.

Light sensitive devices I4, I5 and I6 are either selective of different bands of the spectrum or are rendered selective thereof by the use of color filters. In either case, they will be activated by different portions of the colored light beam to cause the production of separate image currents corresponding in amplitude to the diiferent primary color components which combine to produce the color characteristics of successive elemental areas of the film.

The'driving unit for the film I comprises an element I II conected by a belt and a slip clutch, commonly used in motion picture projectors, coupled by a gearing I I8, having the desired gear ratio, to a shaft I I9 carrying the disc 9.

The disc 9 is mounted on shaft 9 of motor I20 which drives the disc at such speed that each picture carried by the film is completely scanned during one revolution of the disc and within the period of persistence of vision and also drives the film continuously at a rate definitely related to the speed of the disc.

The separate photoelectric or image currents are amplified by the devices II, I8 and I9, respectively, and are supplied to distinct communicating channels 20, 2| and 22, which respectively include, at the receiver, amplifiers 23, 24 and 25.

Amplified currents produced by 23, 24 and 25 are respectively supplied to light sources 26, TI and 28, with which are respectively associated red, green and blue filters 29, 30' and 3|. Light passing through these filters from the sources 26, 21 and 28 is directed into a common path by means of transparent mirrors 32 and 33 in the chamber 34; The composite or mixed beam of light, comprising the three primary colors, is transmitted through lens 35, apertures in the scanning disc 36 and lens 31 to the eye of an observer 0.

Sources 26, 21 and 28 may comprise glow lamps of suitable design, for example, of the type disclosed in a patent of H. W. Weinhart, Patent No. 1,918,309, issued July 18, 1933.

In accordance with well known practice, disc 35 is provided with apertures arranged in a spiral line, which operate to spread out the unit lines, successively scanned at the transmitter, to constitute a complete image in color of each picture carried by the film. Disc 35 is rotated at such speed that a complete image is integrated during each revolution of the disc and at a rate within the period of persistence of vision. Discs 9 and 35 must be operated in phase and in synchronism, and this may be efiected by using a system of the type disclosed in an application of H. M. Stoller, Serial No. 442,564, filed April ,8, 1930.

The gain of therespective amplifiers 23, 24 and 25 is so adjusted and the densities of the up of successive elemental areas in color.

filters 29, 30 and 3| are so chosen that the amount of red, green and blue light is controlled to produce a composite beam of white light, when a white elemental area is being scanned at the transmitter. When a colored elemental area is being scanned at the transmitter the amplitudes of the currents supplied by the amplifiers 23, 24 and 25 will have such relative values that the color oi! the composite beam will be modified to correspond to the color characteristics of successive elemental areas of the transmitted film.

In the system shown in Fig. 2, light of constant intensity from the source I is gathered by the lens 2 to illuminate a section. of a scanning disc 38 provided with apertures 39 arranged in a circle. Light passes through the apertures in the form of a beam, which longitudinally traverses a slot 5 in a mask 6, to illuminate successive elemental areas of unit lines of a film I, which is in continuous motion transversely of the slot 5.

The film I may carry colored pictures produced by the Technicolor or other suitable process, or may embody a representation of a subject in black and white identifying color characteristics, i. e. a film prepared by the Kodacolor or other similar process, and may be moved continuously across the slot 5 at a definite rate, with respect to the speed of disc 38, by a driving unit similar to that included in the system of Fig. 1.

The light beam passes through successive elemental areas of each unit line of the colored representation, if a Technicolor film is used and through a projecting lens 8 to produce a colored image of the elemental areas successively in a single line upon a white screen 40. If a Kodacolor fihn is used, the projecting lens 8 is of the usual type employed for projecting films of this character, i. e., it is provided with a screen carrying red, green and blue filters. These filters cooperate with the lenticular elements of the film to project upon the screen 49 a unit line made In either case the successive unit lines of the representation occupy the same position on the screen 40.

Light reflected from the successive elemental areas of the line projected on the screen 40 activates light sensitive devices 4|, 42 and 43 (the latter being shown as consisting of two elements) each selective of a difierent color, to cause the production of three photoelectric currents. These devices may be inherently selec tive of wave lengths in difierent portions of the spectrum or color filters may be used to render them selective of the respective bands. As shown, devices 4| and 42 may be respectively selective of two bands including different primary colors, while the two-part cell 43 may be selective of a band including a third primary color. Preferably the units 4|, 42 and 43 should each comprise a group of photoelectric cells, selective of the three color bands and should be arranged symmetrically with respect to the screen 40. The cells of the diiferent groups, which are selective of the same band, are connected in parallel to the respective amplifiers II, I8 and I9. As in the system of Fig. 1 the amplified currents supplied by amplifiers I I, I8 and I 9, respectively, are transmitted over channels 20, 2| and 22 to the receiver, therein shown, which is thereby actuated to produce an image in color.

Fig. 3 illustrates a system for transmitting a film I adapted to be moved intermittently, frame by frame, in which each picture is scanned to project an image thereof on the screen 40. This system comprises a constant light source I, a lens sytem 2, a scanning disc 44 provided with apertures arranged in a spiral, a mask 5 having an opening 45 commensurate with the size of the picture, a motion picture film in color or one having color characteristics, a lens 8, screen 40 and units 46, 41 and 48 including groups of light sensitive devices. I

Units 46, 41 and 48 are mounted symmetrically of the screen 40 and are provided with light sensitive devices selective of different primary colors. As indicated by the conductors 49, 50 and 5|, the light sensitive devices of the different units, which are selective of the same color, are connected together and to the respective amplifiers i1, I2 and I9. For example, the red sensitive cells may be connected to conductor 49, over which current is supplied to the amplifier I'I; those sensitive to green may be connected to conductor 50, leading to amplifier l 8, and those sensitive to blue may be connected by conductor 5| to amplifier iii. For

, the sake of clarity, the circuit connecting the group of cells to the respective amplifiers is indicated by a single conductor.

As in the system of Fig. 1, the screen 4|] is illuminated by colored light passing through the successive elemental areas of the picture and is reflected to the light sensitive devices of units 46, 41 and 48, which are th reby activated to cause the production of three distinct image currents which are transmitted over the respective channels to a receiver including three light sources as. shown in Fig. 1.

The spiral of apertures in the disc 44 extend over an angle less than 360 so as to leave between its terminals a blank space, corresponding to the t me period required to shift the film from frame to frame. A disc similar to disc 44 is used at the receiver, which in other respects is identical with that described above.

In Fig. 4 there is shown a source of constant light I, a lens 2 for gathering light from the source I and projecting it upon the periphery of a disc 52 provided with a spiral of apertures, a mask having an opening commensurate with the picture carried by the film I, a lens 8, all of which are identical with similarly identified elements of Fig. 3, for use with a film moved frame by frame.

In addition, there is'provided a lens 53 in the path of the beam of light passing through the apertures of disc 52 and the film 1. This lens serves to focus the beam of light, passing through the difierent elemental areas of the picture, upon a single spot in the screen 54. Associated with the screen and symmetrically positioned with respectthereto are three photoelectric cells, or three groups of cells 55, 56 and 5'! selective of light of different colors.

As in the systems of Figs. 2 or 3, as the case may be, elemental areas of a colored film. or one carrying color characteristics, are successively illuminated and projected in color or with color characterization upon the screen 54' which refiects light to the photoelectric cells which are thereby activated to cause the production of three photoelectric currents which are respectively suppl ed to amplifiers l1, I8 and I9 and transmitted over channels 20, 2| and 22 to the respective light sources 26, 21 and 28 included in a receiver, identical with that disclosed in Fig. 1. This receiver operates to integrate an image correspond ng in color to the picture scanned at the transmitter, which image may be seen by an observer 0.

If the film is moved continuously, a mask 6 with a slot 5 will be used, disc 52 will be similar in design to disc 38, and disc 36 will be used at the receiver. For a film driven frame by frame, the disc 52 will be similar to disc 44 of Fig. 3 and a disc of the same design will be used at the receiver.

In the systems of Figs. 2, 3 and 4 the disc 38, 44 or 52 must be operated in synchronism and in phase with disc 36., This may be accomplished by the system disclosed in the above mentioned Stoller application.

In case the film used at the transmitter is one produced by the Kodacolor process, the image of the pictures carried by it is projected upon the screen 40, or 54, in accordance with motion picture projection practice, through a lens 8 provided with a screen carrying color filters.

Screens 40 and 54 of Figs. 2, 3 and 4 are diffusely reflecting and the light sensitive units 4| to 43, 46 to 48, and 55 to 51, respectively, are mounted in front of the illuminated surface of the screen. However, this invention contemplates the use of screens which are diffusely transmitting, i. e., of material which has been treated to cause the light transmitted therethrough to be radiated in different directions, for example, frosted glass or material provided with lenticulated or prismatic elements. In accordance with this aspect of the invention, the light sensitive units will be similar to those hereinbefore described, but they will be placed behind the screen, i. e., adjacent the surface of the screen opposite to that upon which the beam of light impinges.

The invention is not confined to the use of Technicolor or lenticulated films produced by the Kodacolor process. Other types of colored or lenticulated films or like emulsion carrying material may be used. The term "film is used herein to denote, not only the well known celluloid film, but also forms of emulsion carrying material other than celluloid.

While filters for transmitting primary colors are herein referred to, it is to be understood that these filters are each adapted to transmit a band of colors including one of the primary colors.

Ives application Serial No. 488,304, filed Oct. 13, 1930, discloses a receiver which may be used in place of the receiver herein shown and described.

What is claimed is:

1. An electro-optical system for producing an image in color from a color record comprising a screen, means for successively scanning elemental areas of the record with a moving beam of light passing therethrough to project each area in its natural color upon said screen, and a plurality of light sensitive devices each selective of light of a difierent color band and variably responsive to at least some of the radiations of different wave lengths constituting the band and activated by light reflected from said screen to cause the simultaneous production of a plurality of separate image currents each representative at any instant of a different color characteristic of the area projected.

2. An electro-optical system comprising a transparent photographic color record, a screen, means for successively scanning elemental areas of the record with a moving beam of light passing therethrough to project each area in its natural color upon said screen, and a plurality of light sensitive devices each selective of light of a different color band and variably responsive to at least some of the radiations of different wave lengths constituting the band and activated by light reflected from said screen to cause the simultaneous production of a plurality of separate imageeun'ents each representative at any instant of -a different color characteristic of the areaprojected.v I

3. An electro-optical system comprising a color record, a" screen, means for illuminating and scanning successive elemental areas of each line of said record to produce an illuminated strip in its natural color on said screen, and aplurality of light sensitive devices each selective .of. light of-a-difl'erent color band and variably responsive to-at least some ofthe radiations of diflerent wave lengths constituting the band and activated by. light reflected from said screen to-cause thesimultaneous production of a plurality of separate image currents each representative at any instant of a diflerentcolor characteristic of an elemental area of said strip.

-'-4. An electro-optical systemcomprising a screen, a-transparent photographic color record, .means for continuously moving said record, means for scanning successive elemental areas of said record witha moving beam of light passing therethrough-to project each area in its natural color upon said screen to. produce successive lines which are projected on said screen to occupy ;the same position, and a plurality of light sensitive devices each selective of light of a different .colorband and variably responsive to at least some of the radiations of different wave lengths constituting theiband and activated by light reflected from said screen to cause the simultaneous production of a plurality of separate image cur- ,rents each representative at any instant of a different color. characteristic of the area projected.

5..An electro-optical system for producing an image in 'color from a color record comprising a screen, means for successively-scanning elemental areas of the record with a moving beam of light passing therethrough to project each area in its natural colorupon said screen, and a plurality 01 light sensitive devices each selective of light of a different color band and variably responsive to at least some of the-radiations of different wave lengths constituting the band and activated by light reflected from said screen to cause the simultaneous production of a plurality of separate image currents each representative at any instant of. a diiferent color characteristic of the elemental areas projected, said devices being so located with respect to said screen that the re- .flected light received thereon is substantially the same for-all the elemental areas.

.. .6. electro-optical system for producing an image of atransparent photographic color record comprising a screen, a plurality of light filters of different colors, means for successively scanning elemental areas of the record with a moving beam of light passing therethrough and through said color filters to project each area in its natural color upon said screen, and a plurality of light sensitive deviceseach selective of light of a different color band and variably responsive to at least some of the radiations of different wave lengths constituting the-band and activated by light reflected from said screen to cause the simultaneous production of a plurality of separate image currents each representative at any instant of a diiferent color characteristic of the area projected.

7. An electro-optical system comprising a colored photographic record, ascreen, means for successively scanning. elemental areas or the record with a moving beam of light passing therethrough to project-each area in its natural color upon said screen, and aplurality of light sensitive devices each selective of light of a different color band and variably responsive to at least some of the radiations of different wave lengths constituting the band and activated by light reflected from said screen to cause the simultaneous production of a plurality of separate image currents each representative at any instant of a different color characteristic of the area pro- 8. An electro-optical system comprising a colored photographic record, means for projectingsaid record in its natural color on a screen an elemental area at a time, a plurality of light sensitive devices each selective of light of a different color band and variably responsive to at least some of the radiations of diflerent wave lengths constituting the band and activated by light reflected from said screen to cause the simultaneous production of a plurality of separate image currents each representative at any instant of a different color characteristic of the elemental area projected.

9. An electro-optical system comprising a colored photographic record, means for projecting said record in its natural color on a screen an elemental area at a time so that a plurality of said projected elemental areas occupy the same position on said screen, a plurality of light sensitive devices each selective of light of a different color band and variably responsive to at least some of the radiations of diflferent wave lengths constituting the band and activated by light re- -flected from said screen to cause the simultaneous production of a plurality ofseparate image currents each representative at any instant of a different color characteristic of the elemental area projected.

10. The method of scanning a transparent picture which comprises projecting an elemental spot of light through the picture onto a diflusely reflecting surface, moving said spot over the picture at sufficiently high speed to project the picture in a point-by-point fashion on said surface so that it is visible as a complete picture thereon, and energizing a light sensitive device in accordance with the light of said spot reflected from said surface.

11. The method of scanning a transparent film which includes the steps of illuminating a diffusely reflecting screen with a moving scanning spot from a scanning beam, positioning the transparent film in the path of said beam to modulate the intensity of said spot, whereby said spot projects on said screen, in a point-by-point fashion, an image of the film, and translating the light reflected from said screen into corresponding. photoelectric currents.

12. The method of scanning which comprises producing an elemental spot of light, projecting said spot on a diffusely reflecting surface, modulating said spot in accordance with the shade characteristics of elemental areas of a picture to be transmitted, moving said spot at sufficiently high speed to project on said surface, in a pointby-point fashion an image of the picture to be transmitted, and positioning a light sensitive device adjacent said screen to be energized by the light diffusely reflected therefrom.

13. The method which comprises producing a constant intensity moving scanning spot of elemental area, modulating the intensity of said spot in accordance with the light transmission characteristics of the elemental areas of a picture to be transmitted, interposing in the path of said spot a difiusely reflecting surface, and moving said spot over said surface at sufficiently high speed to produce on said surface, in a pointby-point fashion, an image of the picture to be transmitted, and positioning in front of said surface a light sensitive device to be energized by the light reflected therefrom.

14. In a system of the character described, means for producing a constant intensity scanning spot of elemental area, a diffusely reflecting screen, means for projecting said spot on said screen, means for modulating said spot in accordance with the shade characteristics of elemental areas of a picture to be transmitted, means for moving said spot at a sufficiently high rate of speed to project on said screen, in a pointby-point fashion, an image of the picture to be transmitted, and a light sensitive device energized by the light reflected from said screen.

15. In a system of the character described for obtaining an image of a picture the means for producing a constant intensity light spot of elemental area, a diffusely reflecting screen, means for moving said spot at a sufliciently high speed to scan the picture and simultaneously project on said screen, in a point-by-point fashion, an image of said picture, and a light sensitive device adjacent said screen and energized by the light reflected therefrom.

16. In a system of the character described, means for producing a scanning light spot of elemental area, a diifusely reflecting screen, means for moving said spot over a picture to scan the same in a point-by-point fashion, and simultaneously to project an image of said picture in a point-by-point fashion on said screen,

and a plurality of light sensitive devices energized by the light of said spot reflected from said screen.

17. In a system of the character described, means for producing a concentrated scanning light spot of elemental area, means for moving said spot over a picture to be transmitted to modulate said spot by the shade characteristics of successive elemental areas of the picture, a screen interposed in the path of the modulated light, said spot in moving over said picture simultaneously projecting on said screen an image of the picture in a point-by-point fashion, and a plurality of light sensitive cells energized by the light diffusely reflected from said screen.

18. In a system of the character described, a diffusely reflecting screen, a scanning light spot of elemental area, means for moving said spot to scan a picture film and to simultaneously project, in a point-by-point fashion, an image of said film on said screen, a plurality of light sensitive devices adjacent said screen, and energized by the light diffusely reflected therefrom.

19. In a system of the character described, the

combination of a scanning light spot, a transparent picture film, a diifusely reflecting screen, a television scanner between said spot and screen for moving said spot over said film to scan the film and simultaneously to project on said screen a point-by-point image of said film, and a light sensitive cell positioned to be energized by the light reflected from said screen.

20. A system according to claim 19 in which the scanning spot is moved by means of a scanning device in the form of a spirally perforated disc.

HERBERT E. IVES. 

